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How to create symlink for latest file only?


 
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# 1  
How to create symlink for latest file only?

Hello,

On Solaris 10, here are entries for logs in httpd.conf
Code:
ErrorLog "|/export/apache/apache-2.2.17/bin/rotatelogs -l -f /var/log/apache/error_log.%Y%m%d 86400"

It keeps creating daily logs with below names -
Code:
-rw-r--r--   1 root     root     1016747232 Apr  5 23:59 /var/log/apache/error_log.20190405
-rw-r--r--   1 root     root     946721391 Apr  6 23:59 /var/log/apache/error_log.20190406
-rw-r--r--   1 root     root     1092546540 Apr  7 23:59 /var/log/apache/error_log.20190407
-rw-r--r--   1 root     root     1172486303 Apr  8 23:59 /var/log/apache/error_log.20190408
-rw-r--r--   1 root     root     909466871 Apr  9 23:59 /var/log/apache/error_log.20190409
-rw-r--r--   1 root     root     916731172 Apr 10 23:59 /var/log/apache/error_log.20190410
-rw-r--r--   1 root     root     785326845 Apr 11 23:59 /var/log/apache/error_log.20190411
-rw-r--r--   1 root     root     463003111 Apr 12 13:38 /var/log/apache/error_log.20190412

I want to create a symlink 'error_log' and that should point to latest log file. One idea is, to create two cronjobs for 00:00 midnight, something like this
Code:
00 00 * * * ln -s /var/log/apache/error_log.20190412 /var/log/apache/error_log
59 00 * * * unlink /var/log/apache/error_log

But how will I tell cron, to pick only latest error_log.xxxxxx ? Is it possible ?

Thanks
This User Gave Thanks to solaris_1977 For This Post:
# 2  
Fortunately, your file names are "sort friendly". Try
Code:
ls  *log.* | sort | tail -1

This User Gave Thanks to RudiC For This Post:
# 3  
Yes, that can help. How can I pass that name to cronjob ?

Alternatively I thought of passing same syntax as mentioned in logrotate, but that fails
Code:
bash-3.2# ls -l /var/log/apache/error_log.%Y%m%d
/var/log/apache/error_log.%Y%m%d: No such file or directory
bash-3.2#

If this can work, I can pass that in cron in similar way
Code:
00 00 * * * ln -s /var/log/apache/error_log.%Y%m%d /var/log/apache/error_log
59 00 * * * unlink /var/log/apache/error_log


Last edited by solaris_1977; 04-12-2019 at 06:53 PM..
This User Gave Thanks to solaris_1977 For This Post:
# 4  
shell uses backticks and $( ) to turn program output into strings.

Code:
cd /var/log ; ln -s $(ls  *error_log.* | sort | tail -1) error_log

These 2 Users Gave Thanks to Corona688 For This Post:
# 5  
This worked well. Thanks much
This User Gave Thanks to solaris_1977 For This Post:
# 6  
I'd not bother with the sort. The output should be lexically ordered anyway, so it's redundant.

In some OS, you might need to add a -f to get it to replace the sym-link, and of course you need permission to write to the directory (which root will have, naturally)




Robin
# 7  
Quote:
Originally Posted by Corona688
shell uses backticks and $( ) to turn program output into strings.

Code:
cd /var/log ; ln -s $(ls  *error_log.* | sort | tail -1) error_log

Quote:
Originally Posted by rbatte1
I'd not bother with the sort. The output should be lexically ordered anyway, so it's redundant.

I would also be inclined to use the reverse-sort option to ls, and head instead of tail, thus:
Code:
cd /var/log ; ln -s $(ls -r  *error_log.*  | head -1) error_log

Andrew

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